chemistry_boards review

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chemistry_boards review
2014-09-18 23:44:27
chemistry CP pathology boards

chemistry_boards review
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  1. Red cell acid phosphatase is susceptible to inhibition by ? and resistant to inhibition by ?
    2% formaldehyde; tartrate (like hairy cell leukemia)
  2. What does the mnemonic "bone burns" mean?
    Bone Alkaline Phosphatase is very susceptible to inactivation (90%) by heating/urea
  3. What is the most sensitive marker of hepatic mets? Acute liver dz? Acute rejection after liver transplantation?
    Biliary alk phos; PT (short t1/2 of FVII); GGT (exquisitely sensitive to biliary injury and acute tx shows lymphs attacking bile ducts)
  4. Placental, intestinal, and Regan Alk Phos are significantly inactivated by what compound?
  5. If a Lewis+ type B or O individual ingests a meal, what can be falsely elevated?
    Alk Phos by 30% for 2-12 hrs
  6. What is the role of pyrimidine-5'- nucleotidase in basophilic stippling (seen in lead poisoning, thalassemia, etc.)?
    Pyrimidine-5'- nucleotidase degrades rRNA so when it's deficient you get accumulation of rRNA.
  7. What is the metabolite of codeine and heroin?
  8. The urine opiate immunoassay can detect morphine with varying levels of cross-reactivity to detect codeine, hydrocodone, and hydromorphone. What three opiates cannot be detected due to low cross-reactivity?
    Oxycodone, oxymorphone and meperidine
  9. What is the metabolite of cocaine?
  10. What is the metabolite for combined cocaine and ethanol ingestion?
    Cocaethylene (ethylbenzoylecgonine)
  11. How are lamellar bodies counted? What level predicts lung maturity?
    With platelet channel of a cell counter; >50k/mL
  12. What are the side effects of black licorice (glycyrrhizin) toxicity?
    inhibits 11 beta hydroxysteroid dehydrogenase → mineralcorticoid excess (instead of metabolizing to inactive form) → hypertension and edema
  13. What is the best screening test for primary adrenal hypercotisolism?
    Cushing's evaluation - 1st step is overnight dexameth suppression test or 24 hour urine free cortisol or late night salivary cortisol
  14. What is the final metabolic product of DOPA & dopamine? Norepinephrine and epinehprine? Increased levels of HVA is a marker of what malignancy? VMA?
    HVA; VMA; Neuroblastoma (Low VMA:HVA worse prognosis); pheochromocytoma or neuroblastoma
  15. What is the relationship of TSH to free T4 levels?
    Inverse log-linear so 50% decrease in fT4 causes 100x increase in TSH
  16. What is the major lipid in chylomicrons and VLDL?
  17. What equation allows LDL to be calculated?
    Friedwald: Total chol - HDL - (TG/5)
  18. What is the earliest lab value that confirms the diagnosis of iron deficiency anemia? What values change subsequently?
    ↓ serum ferritin (usu 10micrograms/L); followed by ↓TIBC, ↓ serum iron, and ↑Zinc protoporphyrin → ↓Hb → normocytic normochromic anemia → microcytic, hypochromic anemia
  19. All of the following are clinical features of iron deficiency anemia except:
    A) Thrombocytosis
    B) Koilonychia (spoon nails)
    C) Atrophic Glossitis
    D) Cheilitis or Plummer-Vinson Syndrome
    E) Pellagra
    E - associated with niacin def
  20. How much Fe is in 1 mL of pRBCs? 1mL of whole blood?
    1 mg; 0.5 mg
  21. Where is Fe predominantly absorbed in the gut?
  22. What important role does folate play in the body? B12?
    • Folate - active form is tetrahydrofolate (THF), a cofactor in methyl transfers in DNA synthesis so deficiency → impaired nuclear maturation
    • B12 - cofactor for methyltransferase to convert circulating methylfolate to THF & methylmalonyl CoA mutase to convert methylmalonyl CoA to succinyl CoA
  23. What chemistry findings are seen in vitamin B12 deficiency vs. folate deficiency?
    Basically the same: ↑LDH (hemolytic anemia from ineffective erythropoiesis), ↑ serum urinary formiminoglutamic acid (FIGLU) - an intermediate in histidine metabolism, and ↓serum [folate or B12] , and ↓RBC folate (2/3 of B12 def cases)
  24. What two substances detected in the urine are increased in B12 deficiency? Which one is present in normal levels in folate deficiency, and thus can help distinguish the two?
    Homocysteine methylmalonic acid (MMA); MMA is only elevated in B12 def
  25. B12 is a cofactor for methyltransferase enzymes. Which two substrates accumulate in B12 deficiency?
    Methylfolate and methylmalonyl CoA
  26. What important methyl transfer in DNA synthesis happens with folate?
    • dUMP to dTMP with methyl transfer via THF
    • Deficiency → impaired nuclear maturation → nuclear:cyto dyssynchrony
  27. Name two hematologic-related diseases that has neurologic complications.
    • 1) B12 deficiency
    • 2) TTP/HUS
  28. How is B12 absorbed from the diet into the bloodstream? What protein is it bound to in circulation?
    Bound to R factor in stomach → pancreatic enzymes release B12 from R factor to bind IF in duodenum → IF-B12 absorbed in ileum and B12 bound to transcobalamin I & II within enterocytes → bloodstream
  29. All of the following are manifestations of pernicious anemia except:
    A) Chronic atrophic gastritis
    B) Gastric atrophy
    C) Achlorhydria (2/2 hypergastrinemia)
    D) Autoimmune destruction of gastric chief cells
    E) Anti-IF or anti-parietal cell antibodies
    D - parietal cells are destroyed
  30. In pernicious anemia, which antibodies are more sensitive? More specific?
    • Sensitive - anti-parietal
    • Specific - anit-IF
  31. T/F: B12 deficiency can produce a falsely low RBC folate level.
    True, in ~50% of patients
  32. Which of the following can lead to a falsely normal serum B12? Falsely low serum B12?
    1) MPD
    2) Pregnancy
    3) Myeloma
    4) Haptocorrin/Transcobalamin I deficiency
    5) HIV
    6) Transcobalamin II deficiency
    7) Liver disease
    • 1, 6, 7 = falsely normal serum B12
    • 2, 3, 4, 5 = falsely low serum B12
  33. How does the Schilling test work?
    • I) Saturate with radioactive B12, collect 24 hour urine; low radioactive levels confirms malabsorption because if absorbed by gut, would've been excreted in urine
    • II) Radiactive B12 + IF, remeasure for absorption
  34. What conditions cause a decrease in alkaline phosphatase?
    Hypophosphatemia and malnutrition
  35. What conditions can cause increased alkaline phosphatase?
    • 1) Paget's dz of bone
    • 2) hepatic mets
    • 3) bone mets
    • 4) biliary dz
    • 5) bone growth in kids
    • 6) pregnancy
  36. What does an elevated urine porphobilinogen indicate? elevated urine porphyrins?
    Acute porphyria crisis/attack (it's pathognomonic!); porphyria cutanea tarda
  37. Why is anti-streptolysin O a good test for evaluating post-strep glomerulonephritis?
    It develops 1-4 wks after an initial strep infxn
  38. In gas chromatography, what does derivatization do?
    Makes the molecules less polar, thus more volatile
  39. On the Hb dissociation curve, does the curve shift left or right with decreased 2,3 DPG? What is 2,3 DPG? What does 2,3 DPG bind to on the RBC?
    Shift left (increased affinity); increased in hypoxic state; binds beta globulins
  40. What shifts the Hb dissociation curve to the left?
    Decreased temp, CO, increased pH, and decreased 2,3 DPG